U.S. patent number 6,238,524 [Application Number 09/211,363] was granted by the patent office on 2001-05-29 for rotating plate heat exchanger.
This patent grant is currently assigned to Ovation Products Corporation. Invention is credited to William H. Zebuhr.
United States Patent |
6,238,524 |
Zebuhr |
May 29, 2001 |
Rotating plate heat exchanger
Abstract
The invention relates to an improved evaporator and condenser
unit for use in distilling a liquid such as water. The evaporator
and condenser unit includes a plurality of stacked, spaced-apart
plates disposed within a housing. The plates are horizontally
arranged around a common, vertical axis for rotation. Adjacent
plates define spaces between their oppositely facing surfaces,
which are alternating configured as evaporating and condensing
chambers. An outlet tube transfers vapor generated within the
housing to a compressor and an inlet tube delivers compressed vapor
to central receiving space within the stack of plates. A sump
containing the liquid to be distilled is located at a lower portion
of the housing. Each plate includes a plurality of ports for
distributing liquid to be distilled and for extracting a
condensate. In particular, each plate includes at least one liquid
feed port that provides a generally vertical liquid flow path
through each evaporating chamber, by-passing the adjacent
condensing chambers. A rotary scoop tube draws liquid from the sump
and distributes it to each of the evaporating chambers. A
condensate port within each plate provides a generally vertical
condensate flow path through each condensing chamber, by-passing
the evaporating chambers. The inner diameter ends of the condensing
chambers are open to receive the compressed vapor and the outer
diameter ends of the evaporating chambers are open to transfer
vapor and remaining liquid to the housing. A stationary scoop tube
removes condensate generated within the condensing chambers of the
unit.
Inventors: |
Zebuhr; William H. (Nashua,
NH) |
Assignee: |
Ovation Products Corporation
(Nashua, NH)
|
Family
ID: |
22786625 |
Appl.
No.: |
09/211,363 |
Filed: |
December 14, 1998 |
Current U.S.
Class: |
202/185.1;
159/18; 159/6.1; 165/88; 202/172; 203/24 |
Current CPC
Class: |
B01D
1/223 (20130101); B01D 1/26 (20130101); B01D
1/28 (20130101); B01D 5/0015 (20130101); F28D
9/0025 (20130101); F28D 9/0043 (20130101); F28D
11/02 (20130101); F28F 2245/02 (20130101) |
Current International
Class: |
B01D
5/00 (20060101); B01D 1/00 (20060101); B01D
1/26 (20060101); B01D 1/22 (20060101); B01D
1/28 (20060101); B01D 001/26 (); B01D 003/00 ();
B01D 003/02 () |
Field of
Search: |
;159/28.6,6.1,18,24.1
;165/165,88,166 ;202/238,172,173,174,182,185.1 ;203/24,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Beck; Shrive
Assistant Examiner: Varcoe; Frederick
Attorney, Agent or Firm: Cesari and McKenna, LLP
Claims
What is claimed is:
1. An evaporator-and-condenser unit for use in a vapor compression
distiller comprising:
A. a motor;
B. a compressor having a compressor inlet and a compressor
outlet;
C. a heat exchanger coupled to the motor for rotation thereby about
an axis of rotation and comprising:
1. first and second end plates having respective inner faces;
and
2. a plate stack connected between the first and second end plates
and including a plurality of spaced-apart heat-exchange plates,
each heat-exchange plate having a center point and an axis that
passes through the plate's center point and extends perpendicular
to a nominal plane of the plate, the axes of the plates coaxially
aligned with the axis of rotation, each heat-exchange plate having
two plate surfaces and inner and outer edges with respect to the
center point, the heat-exchange plates defining alternating
evaporating and condensing chambers between their opposing plate
surfaces such that the plate surfaces between which the condensing
chambers are defined cooperate with the inner faces of the first
and second end plates to define a generally closed interior
condensation space in fluid communication with the compressor
outlet, wherein:
a) each pair of heat-exchange plates that defines a condensing
chamber is sealed at those heat-exchange plates' outer edges and
cooperates to form near their inner edges a liquid feed passage
isolated from the condensing chamber that they define but
cooperating with the evaporating chambers and the other liquid feed
passages to form a liquid feed path by which feed liquid can be
introduced into the evaporating chambers; and
b) each pair of heat-exchange plates that defines an evaporating
chamber is sealed at those heat-exchange plates' inner edges and
cooperates to form near their outer edges a condensate passage
isolated from the evaporating chamber that they define but
cooperating with the condensing chambers and the other condensate
passages to form a condensate flow path by which condensate can be
withdrawn from the condensing chambers; and
D. a side wall disposed circumferentially about the heat exchanger
and forming with the plate surfaces between which the evaporating
chambers are defined an evaporator space in fluid communication
with the compressor inlet.
2. The evaporator and condenser unit of claim 1 further comprising
a restriction element disposed in one or more evaporating chambers
for distributing liquid received from the liquid feed path along
the opposing plate surfaces of the respective evaporating
chamber.
3. The evaporator and condenser unit of claim 2 wherein the
restriction element comprises a pair of opposing protrusions
extending from the plate surfaces of the evaporation chamber, the
opposing protrusions defining a gap through which the feed liquid
flows.
4. The evaporator and condenser unit of claim 3 wherein the
restriction element is radially located outboard of the liquid feed
passage relative to the axis of rotation and extends
circumferentially around the evaporation chamber.
5. The evaporator and condenser unit of claim 2 wherein each pair
of heat-exchange plates that defines a condensing chamber is open
at those heat-exchange plates' inner edges to a central receiving
space that is coupled to the compressor outlet by a first tube.
6. The evaporator and condenser unit of claim 5 wherein each pair
of heat-exchange plates that defines an evaporating chamber is open
at those heat-exchange plates' outer edges to a vapor receiving
space that is coupled to the compressor inlet by a second tube.
7. The evaporator and condenser unit of claim 6 wherein the motor
includes a shaft that is received at one of the first and second
end plates.
8. The evaporator and condenser unit of claim 6 wherein the heat
exchanger further comprises a sump disposed proximate to the second
end plate opposite the plate stack, the sump containing a liquid to
be distilled and in fluid communication with the liquid feed
passages of the evaporating chambers.
9. The evaporator and condenser unit of claim 8 wherein the heat
exchanger further comprises a rotary scoop tube extending from the
liquid feed passage of at least one evaporating chamber, through
the second end plate and into the sump, the rotary scoop tube
having an end and being arranged upon rotation to convey liquid
from the sump to the liquid feed passage at the at least one
evaporating chamber.
10. The evaporator and condenser unit of claim 6 wherein the heat
exchanger further comprises:
a flange cooperating with the first end plate to define a
condensate collection space that is in fluid communication with the
condensate feed passages of the condensing chambers; and
a stationary scoop tube extending into the condensate collection
space, the stationary scoop tube having an end and being arranged
to withdraw condensate from the condensate collection space.
11. The evaporator and condenser unit of claim 6 wherein each
heat-exchange plate includes at least one condensate port proximate
to its outer edge, the condensate ports of the plate stack
cooperate to form the condensate passage through the condensing
chambers.
12. The evaporator and condenser unit of claim 11 wherein each
heat-exchange plate includes at least one liquid feed port
proximate to its inner edge, the liquid feed ports of the plate
stack cooperate to form the liquid feed passage through the
evaporating chambers.
13. The evaporator and condenser unit of claim 12 wherein each
heat-exchange plate includes a condensate port flange around its at
least one condensate port in the respective evaporating chamber,
each condensate port flange having a distal end such that the
distal ends of opposing condensate port flanges of a given
evaporating chamber are joined in sealing engagement.
14. The evaporator and condenser unit of claim 13 wherein each
heat-exchange plate further includes a feed port flange around its
at least one liquid feed port in the respective condensing chamber,
each feed port flange having a distal end such that the distal ends
of opposing feed port flanges in a given condensing chamber are
joined in sealing engagement.
15. A heat exchanger for use in a distiller having a compressor, a
side wall disposed circumferentially about the heat exchanger, and
a motor coupled to the heat exchanger for rotation thereby about an
axis of rotation, the compressor including a compressor inlet and a
compressor outlet, the heat exchanger comprising:
A. first and second end plates having respective inner faces;
and
B. a plate stack connected between the first and second end plates
and including a plurality of spaced-apart heat-exchange plates,
each heat-exchange plate having a center point and an axis that
passes through the plate's center point and extends perpendicular
to a nominal plane of the plate, the axes of the plates coaxially
aligned with the axis of rotation, each heat-exchange plate having
two plate surfaces and inner and outer edges with respect to the
center point, the heat-exchange plates defining alternating
evaporating and condensing chambers between their opposing plate
surfaces such that the plate surfaces between which the condensing
chambers are defined cooperate with the inner faces of the first
and second end plates to define a generally closed interior
condensation space in fluid communication with the compressor
outlet, wherein:
1. each pair of heat-exchange plates that defines a condensing
chamber is sealed at those heat-exchange plates' outer edges and
cooperates to form near their inner edges a liquid feed passage
isolated from the condensing chamber that they define but
cooperating with the evaporating chambers and the other liquid feed
passages to form a liquid feed path by which feed liquid can be
introduced into the evaporating chambers; and
2. each pair of heat-exchange plates that defines an evaporating
chamber is sealed at those heat-exchange plates' inner edges and
cooperates to form near their outer edges a condensate passage
isolated from the evaporating chamber that they define but
cooperating with the condensing chambers and the other condensate
passages to form a condensate flow path by which condensate can be
withdrawn from the condensing chambers; and
3. the side wall forming with the plate surfaces between which the
evaporating chambers are defined an evaporator space in fluid
communication with the compressor inlet.
16. The heat exchanger of claim 15 further comprising a restriction
element disposed in one or more evaporating chambers for
distributing liquid received from the liquid flow path along the
opposing plate surfaces of the respective evaporating chamber.
17. The heat exchanger of claim 16 wherein the restriction element
comprises a pair of opposing protrusions extending from the plate
surfaces of the respective evaporation chamber, the opposing
protrusions defining a gap through which the feed liquid flows.
18. The heat exchanger of claim 17 wherein the restriction element
is radially located outboard of the liquid feed passage relative to
the axis of rotation and extends circumferentially around the
evaporation chamber.
19. The heat exchanger of claim 16 wherein each pair of
heat-exchange plates that defines a condensing chamber is open at
those heat-exchange plates' inner edges to a central receiving
space, the central receiving space capable of receiving compressed
vapor from the compressor outlet.
20. The heat exchanger of claim 19 wherein each pair of
heat-exchange plates that defines an evaporating chamber is open at
those heat-exchange plates' outer edges to a vapor receiving space,
the vapor receiving space capable of providing vapor to the
compressor inlet.
21. The heat exchanger of claim 20 wherein the motor includes a
shaft that is received at one of the first and second end
plates.
22. The heat exchanger of claim 20 further comprising a sump
disposed proximate to the second end plate opposite the plate
stack, the sump containing a liquid to be distilled and in fluid
communication with the liquid feed passages of the evaporating
chambers.
23. The heat exchanger of claim 22 further comprising a rotary
scoop tube extending from the liquid feed passage of at least one
evaporating chamber, through the second end plate and into the
sump, the rotary scoop tube having an end and being arranged upon
rotation to convey liquid from the sump to the liquid feed passage
at the at least one evaporating chamber.
24. The heat exchanger of claim 15 further comprises:
a flange cooperating with the first end plate to define a
condensate collection space that is in fluid communication with the
condensate feed passages of the condensing chambers; and
a stationary scoop tube extending into the condensate collection
space, the stationary scoop tube having an end and being arranged
to withdraw condensate from the condensate collection space.
25. The heat exchanger of claim 15 wherein each heat-exchange plate
includes at least one condensate port proximate to its outer edge,
the condensate ports of the plate stack cooperate to form the
condensate passage through the condensing chambers.
26. The heat exchanger of claim 25 wherein each heat-exchange plate
includes at least one liquid feed port proximate to its inner edge,
the liquid feed ports of the plate stack cooperate to form the
liquid feed passage through the evaporating chambers.
27. The heat exchanger of claim 26 wherein each heat-exchange plate
includes a condensate port flange around its at least one
condensate port in the respective evaporating chamber, each
condensate port flange having a distal end such that the distal
ends of opposing condensate port flanges of a given evaporating
chamber are joined in sealing engagement.
28. The heat exchanger of claim 27 wherein each heat-exchange plate
further includes a feed port flange around its at least one liquid
feed port in the respective condensing chamber, each feed port
flange having a distal end such that the distal ends of opposing
feed port flanges in a given condensing chamber are joined in
sealing engagement.
29. A multiple-effect heat exchanger for use in a distiller having
a compressor, a side wall disposed circumferentially about the heat
exchanger, and a motor coupled to the heat exchanger for rotation
thereby about an axis of rotation, the compressor including a
compressor inlet and a compressor outlet, the heat exchanger
comprising:
first and second end plates having respective inner faces;
a plurality of effects, including a first and a last effect,
disposed between the first and second end plates, each effect
comprising:
a plate stack including a plurality of spaced-apart heat-exchange
plates, each heat-exchange plate having a center point and an axis
that passes through the plate's center point and extends
perpendicular to a nominal plane of the plate, the axes of the
plates coaxially aligned with the axis of rotation, each
heat-exchange plate having two plate surfaces and inner and outer
edges with respect to the center point, the heat-exchange plates
defining alternating evaporating and condensing chambers between
their opposing plate surfaces such that the plate surfaces between
which the condensing chambers are defined cooperate with the inner
faces of the first and second end plates to define a generally
closed interior condensation space in fluid communication with the
compressor outlet;
an inner wall mounted to the first end plate inboard of the inner
edges of the plates relative to the axis of rotation and extending
along all but the first effect;
an outer wall mounted to the second end plate between the outer
edges of the plates and the side walls of the housing and extending
along all but the last effect; and
at least one transition plate disposed between each pair of
adjacent plate stacks; wherein
1. each pair of heat-exchange plates that defines a condensing
chamber is sealed at those heat-exchange plates' outer edges and
cooperates to form near their inner edges a liquid feed passage
isolated from the condensing chamber that they define but
cooperating with the evaporating chambers and the other liquid feed
passages to form a liquid feed path by which feed liquid can be
introduced into the evaporating chambers;
2. each pair of heat-exchange plates that defines an evaporating
chamber is sealed at those heat-exchange plates' inner edges and
cooperates to form near their outer edges a condensate passage
isolated from the evaporating chamber that they define but
cooperating with the condensing chambers and the other condensate
passages to form a condensate flow path by which condensate can be
withdrawn from the condensing chambers;
3. each transition plate cooperates to form near their inner and
outer edges corresponding first and second weirs, the first weir
isolating the respective evaporating chambers and the second weir
isolating the respective condensing chambers of the adjacent
effect;
4. the inner and outer walls cooperate with each transition plate
to form a corresponding transition space providing fluid
communication between the evaporating chambers of a first effect
and the condensing chambers of a next highest effect; and
5. the side wall forming with the plate surfaces between which the
evaporating chambers are defined at the last effect an evaporator
space in fluid communication with the compressor inlet.
30. The multiple-effect heat exchanger of claim 29 further
comprising a restriction element disposed in one or more
evaporating chambers for distributing liquid received from the
liquid feed path along the opposing plate surfaces of the
respective evaporating chamber.
31. The multiple-effect heat exchanger of claim 30 wherein the
restriction element comprises a pair of opposing protrusions
extending from the plate surfaces of the respective evaporation
chamber, the opposing protrusions defining a gap through which the
feed liquid flows.
32. The multiple-effect heat exchanger of claim 31 wherein the
restriction element is radially located outboard of the liquid feed
passage relative to the axis of rotation and extends
circumferentially around the evaporation chamber.
33. The multiple-effect heat exchanger of claim 30 further
comprising a sump disposed proximate to the second end plate
opposite the plate stack, the sump containing a liquid to be
distilled and in fluid communication with the liquid feed passages
of the evaporating chambers.
34. The multiple-effect heat exchanger of claim 33 further
comprising a rotary scoop tube extending from the liquid feed
passage of at least one evaporating chamber through the second end
plate and into the sump, the rotary scoop tube having an end and
being arranged upon rotation to convey liquid from the sump to the
liquid feed passage at the least one evaporating chamber.
35. The multiple-effect heat exchanger of claim 34 further
comprising:
a flange cooperating with the first end plate to define a
condensate collection space that is in fluid communication with the
condensate feed passages of the condensing chambers; and
a stationary scoop tube extending into the condensate collection
space, the stationary scoop tube having an end and being arranged
to withdraw condensate from the condensate collection space.
36. The multiple-effect heat exchanger of 35 wherein each
heat-exchange plate includes at least one condensate port proximate
to its outer edge, the condensate ports of the plate stack
cooperate to form the condensate passage through the condensing
chambers.
37. The multiple-effect heat exchanger of claim 36 wherein each
heat-exchange plate includes at least one liquid feed port
proximate to its inner edge, the liquid feed ports of the plate
stack cooperate to form the liquid feed passage through the
evaporating chambers.
38. The multiple-effect heat exchanger of claim 37 wherein each
heat-exchange plate includes a condensate port flange around its at
least one condensate port in the respective evaporating chamber,
each condensate port flange having a distal end such that the
distal ends of opposing condensate port flanges of a given
evaporating chamber are joined in sealing engagement.
39. The multiple-effect heat exchanger of claim 38 wherein each
heat-exchange plate further includes a feed port flange around its
at least one liquid feed port in the respective condensing chamber,
each feed port flange having a distal end such that the distal ends
of opposing feed port flanges in a given condensing chamber are
joined in sealing engagement.
40. The multiple-effect heat exchanger of claim 33 wherein the
outer wall has a plurality of apertures providing fluid
communication between the evaporating chambers and the sump.
41. The multiple-effect heat exchanger of claim 40 wherein the
outer wall has an inner surface relative to outer edges of the
heat-exchange plates and further wherein the plurality of apertures
are sized so as to cause an annular pool of condensate to form on
the inner surface of the outer wall, the annular pool presenting a
vapor barrier to the flow of vapor through the plurality of
apertures.
Description
BACKGROUND OF THE INVENTION
This invention relates to distillation systems and, more
specifically, to an improved, highly efficient, rotary evaporator
and condenser for use in a vapor compression distiller.
Distillation is a common method for generating potable water from
otherwise unsafe water sources (such as sea water or polluted
ground water). With distillation, water is heated to boiling and
the corresponding vapor (i.e., steam) is collected and condensed,
producing distilled water. Many contaminants that are present in
the water source are left behind when the water is converted to its
vapor phase. Conventional small distillers typically incorporate an
electric heating element to boil water in a tank. A condensing coil
mounted above the tank collects the vapor and condenses it. The
distilled water is then transferred to a holding tank or cell.
These boiler-type distillers, however, require substantial amounts
of electrical power to produce relatively little distilled water
and are thus highly inefficient. They are also extremely slow,
often taking many hours to produce just a few gallons of distilled
water. Accordingly, boiling-type distillers have not gained
widespread acceptance or use.
In addition to boiler-type distillers, thin-film distillers have
also been proposed. For example, U.S. Pat. No. 4,402,793 to Petrek
et al. titled MULTIPLE EFFECT THIN FILM DISTILLATION SYSTEM AND
PROCESS is directed to a solar-powered, thin film distiller. In the
distiller of the '793 patent, a plurality of parallel, spaced-apart
plates are arranged to face the sun. Water to be distilled is
supplied to the tops of the plates and guided to run down the back
face of each plate. Sunlight irradiating the first plate's front
side heats the plate and causes a portion of the water running down
the opposite side to evaporate. The vapor condenses along the front
side of the next adjacent plate, transferring heat to the flow of
water on its opposite side and so on. Condensate generated along
the front sides of the plates is separately collected at the
bottoms of the plates.
To improve the efficiency of thin-film distillers, rotary
evaporators have also been designed. For example, U.S. Pat. No.
4,731,159 to Porter et al., entitled EVAPORATOR, is directed to a
rotary type evaporator having a plurality of horizontally stacked
annular plates that are disposed within a housing and mounted for
rotation about a central shaft. The ends of alternating pairs of
plates are sealed to define sealed spaces. Thus, each sealed space
includes two inner plate surfaces facing each other and two outer
surfaces, each of which is opposite a respective inner surface. The
sealed spaces, moreover, are interconnected by a series of orifices
and washers disposed between adjacent outer plate surfaces. A
liquid to be distilled is introduced into the stack of rotating
annular plates and enters each of the sealed spaces through an
inlet port. As the liquid enters the spaces, it flows along the
opposing inner surfaces of the space. A condensable vapor is
introduced into the housing and is thus free to flow around the
outer surfaces of the plates. The vapor is not, however, able to
enter the sealed spaces. Since the liquid in the sealed spaces is
at a lower temperature than the vapor, the vapor condenses along
the outer surfaces of the plates. The condensate is thrown off of
the rotating plates, collects inside the housing and is removed
through an outlet port located in the bottom of the housing.
Condensation of the vapor also transfers heat across the plates to
the liquid, thereby causing a portion of the liquid in the sealed
spaces to evaporate. The vapor exits the sealed spaces through the
liquid inlet ports and is removed from the top of the housing. Any
non-evaporated liquid remaining in the spaces flows upwardly along
the sealed spaces through the corresponding orifice/washer
arrangements and is also withdrawn from the top of the
evaporator.
Although it may provide some advantages, the design of the '159
evaporator presents a substantial risk of contamination of the
condensate by the liquid being evaporated and is thus not suitable
to generating potable distilled water. In other words, with the
evaporator of the '159 patent, the unsafe water which is being
distilled is capable of mixing with and thus contaminating that
distillate. More specifically, any leak at a sealed space would
allow liquid from the sealed space to enter the housing and mix
with the distillate being collected therein. The likelihood of such
an occurrence, moreover, is not insignificant due to the corrosive
attributes of some water sources and the high number of orifices
and washers that are needed to provide fluid communication between
the various sealed spaces.
Multiple-effect distillation systems are also known. U.S. Pat. No.
2,894,879 to Hickman entitled MULTIPLE EFFECT DISTILLATION
discloses a distiller having fifteen vertically arranged effects.
Each effect includes a rotating evaporator section and an
associated condenser section. The liquid to be distilled is
supplied to the evaporator section of the first stage, which is
located at the top of the distiller. A heat source, such as steam,
is similarly provided to the condenser section of the first effect,
in order to evaporate at least a portion of the liquid. The vapor
generated in the evaporator section of the first effect is then
transferred to the second effect condenser section where it is used
to heat liquid left over from the first effect that is likewise
provided to the evaporator section of the second effect. The
distillate generated within the condenser section of the first
effect is also transferred to the condenser section of the second
effect. This process is repeated at each effect of the distiller.
The distillate accumulated from each of the effects is then removed
from the system. To achieve the desired flow among the effects, the
distiller of the '879 patent includes numerous rotating tubing
segments that are used to interconnect the various evaporator and
condenser sections and to spray liquid onto the surface of the
evaporator sections. Accordingly, the manufacturing and assembly
costs of the system are relatively high. Furthermore, any leaks of
liquid in the evaporator sections will contaminate distillate being
collected in the adjacent condenser sections. The existence of any
such leaks, moreover, would be extremely difficult to detect.
Vapor compression distillers, which can be more efficient than
conventional distillers, are also known. The underlying principle
of vapor compression distillers is that, by raising the pressure of
a vapor (e.g., steam), its saturation temperature also rises. In
the vapor compression distiller, vapor produced in an evaporator is
removed, compressed (raising its saturation temperature) and
returned to the evaporator where it condenses, producing a
distillate. Furthermore, the heat of vaporization that is given off
as the vapor (having a raised saturation temperature) condenses is
used to heat (and thus evaporate) the liquid being distilled.
Large-scale vapor compression distillers using powerful
censtrifugal compressors can produce hundreds of gallons of
distilled water a day. These distillers, however, do not scale
well. That is, for installations requiring only tens of gallons of
distilled water a day, large-scale distillers are impractical, in
part, due to the operating costs associated with the centrifugal
compressor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a rotary
evaporator and condenser for use in a distiller.
It is a further object of the present invention to provide an
evaporator and condenser that reduces the risk of contamination of
the final condensate.
A further object of the present invention is to provide a
multiple-effect evaporator and condenser unit.
A still further object of the present invention is to provide a
multiple-effect evaporator and condenser that reduces the risk of
contamination of the final condensate.
Briefly, the invention relates to an improved evaporator and
condenser unit for use in distilling a liquid such as water. The
evaporator and condenser unit includes a plurality of stacked,
spaced-apart plates disposed within a housing. The plates are
horizontally arranged around a common, vertical axis for rotation.
Adjacent plates define spaces between their oppositely facing
surfaces and the spaces are alternating configured as evaporating
and condensing chambers. The unit further includes an outlet tube
that transfers vapor generated within the housing to a compressor
and an inlet tube that delivers compressed vapor to central
receiving space within the stack of plates. A sump containing the
liquid to be distilled is located at a lower portion of the
housing. Each plate includes a plurality of ports for distributing
liquid to be distilled and for extracting a condensate. In
particular, each plate includes at least one liquid feed port
disposed at a inner diameter position that provides a generally
vertical liquid flow path through each evaporating chamber,
by-passing the adjacent condensing chambers. A rotary scoop tube
extends into the sump and is coupled to the lowest evaporating
chamber at its liquid feed port. Each plate also includes at least
one condensate port disposed at an outer diameter position that
provides a generally vertical condensate flow path through each
condensing chamber, by-passing the evaporating chambers. The inner
diameter ends of the evaporating chambers, moreover, are sealed,
while the inner diameter ends of the condensing chambers, are open
to receive the compressed vapor. Similarly, the outer diameter ends
of the evaporating chambers are open to the housing, while the
outer diameter ends of the condensing chambers are sealed. A
stationary scoop tube extends into a condensate collection area at
the upper most condensing chamber.
In operation, the stack of plates are rotated causing the rotary
scoop tube to draw liquid upwardly from the sump to the lowest
evaporating chamber. The liquid is distributed along the liquid
flow path from the lowest evaporating chamber upwardly through each
of the remaining evaporating chambers. As liquid reaches each
evaporating chamber, it is forced outwardly due to the centrifugal
forces generated by the rotating plates. A restriction element at
the entrance to each evaporating chamber forces the liquid to flow
in sheet form along the oppositely facing surfaces of each
evaporating chamber. As it flows along the plate surfaces, a
portion of the liquid transforms to vapor, which enters the housing
as the evaporating chambers are open at their outer diameter ends.
The vapor is then drawn upwardly through the outlet tube and into
the compressor. Any remaining liquid in the evaporating chambers is
flung off of the corresponding plate surfaces, strikes the side
walls of the housing and drops down into the sump. Compressed vapor
is delivered by the inlet tube to the stack of rotating plates at
the central receiving space. As the condensing chambers are open at
their inner diameter ends, compressed vapor enters each condensing
chamber. Compressed vapor condenses along the oppositely facing
surfaces of the each condensing chamber and the condensate is
forced to the outer ends of the condensing chambers which are
sealed. The condensate from each condensing chamber flows upwardly
through the stack of plates along the condensate flow path and is
withdrawn from the housing by the stationary scoop. As compressed
vapor condenses in the condensing chambers, the corresponding heat
of vaporization is transferred through the plates to the adjacent
evaporating chambers where it is used to vaporize liquid flowing
along the other side of the plate which is located in the adjacent
evaporating chamber.
In an alternative embodiment, the evaporator and condenser unit
provides multiple condensing and evaporating effects. More
specifically, a plurality of evaporator/condenser effects are
preferably arranged in vertical stack. Each effect includes a
plurality of stacked, spaced-apart plates such that adjacent plates
define spaces between their oppositely facing surfaces and the
spaces are alternating configured as evaporating and condensing
chambers. An outlet tube transfers vapor in the housing to a
compressor, where it is compressed and returned to a central
receiving space associated with the first effect. A sump containing
the liquid to be distilled is located at a lower portion of the
housing proximate to the first effect. Each of the plates within a
single effect includes at least one liquid feed port disposed at a
inner diameter position that provides a generally vertical liquid
flow path through each evaporating chamber and at least one
condensate port disposed at an outer diameter position that
provides a generally vertical condensate flow path through each
condensing chamber. A rotary scoop tube extends into the sump from
the liquid feed port at the first evaporating chamber of the first
effect. The inner diameter ends of the evaporating chambers are
sealed, while the inner diameter ends of the condensing chambers
are open to receive compressed vapor. Similarly, the outer diameter
ends of the evaporating chambers are open, while the outer diameter
ends of the condensing chambers are sealed. Disposed between each
effect is one or more transfer plates that includes at least one
liquid transfer port and at least one condensate transfer port. The
ports of the transfer plates are radially aligned but axially
off-set from the respective ports of the adjacent effects so as to
define an inner weir and an outer weir at the interfaces between
each effect. The multiple-effect unit also includes an outer wall
that is disposed between the outer edges of the plates and the
housing side walls along all but the highest effect and an inner
wall that is disposed between the inner edges of the plates and the
axis of rotation along all but the lowest effect. At least one
aperture is formed through the outer wall at each effect. A
stationary scoop tube extends into a condensate collection area at
the highest effect.
In operation, the flow of liquid, vapor, compressed vapor and
condensate within each effect is generally the same as described
above in connection with the single effect system. For example,
rotation of the plates causes the first scoop to draw liquid
upwardly from the sump along the liquid flow path within the first
effect and thus to each of the corresponding evaporating chambers.
Within the evaporating chambers, liquid flows along the opposing
plate surfaces and a portion thereof evaporates. Excess liquid from
the evaporating chambers of all but the highest effect, rather than
entering the housing, instead collects inside of the outer wall
where it forms an annular pool. A stream of liquid from the annular
pool flows through the apertures, enters the housing and collects
at the sump. The presence of this annular pool, however, blocks the
vapor generated in the evaporating chambers from also flowing
through the apertures and entering the housing. Liquid from the
liquid flow path in the first effect also crosses the transfer
plate and enters the liquid flow path in the next higher effect. At
the transfer plate, however, the liquid must climb over the inner
weir in order to reach the liquid flow path of the next higher
effect. As a result, a column of liquid, having the same height as
the weir is formed, blocking higher pressure vapor at the lower
effects from simply flowing to the higher effects which are
operating at lower vapor pressures. Instead, the vapor is conveyed
inwardly along the transfer plate to the open inner diameter ends
of the condensing chambers of the next highest effect. The vapor
condenses in this next highest effect generating a condensate and
transferring heat to the adjacent evaporating chambers.
Additionally, the condensate generated within each effect flows
upwardly along the condensate flow path and is similarly forced to
climb over the outer weir formed at each transfer plate, blocking
higher pressure vapor at the lower effects from flowing to the
higher effects. This flow pattern is repeated at and between each
effect up until the highest effect. At the highest effect, there is
no outer wall. Therefore, the vapor generated in the corresponding
evaporating chambers simply enters the housing and is transferred
to the compressor, and any un-evaporated liquid simply falls back
to the sump. At the highest effect, the condensate generated by
each effect is withdrawn by the stationary scoop tube.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and further advantages of the invention may be better
understood by referring to the following description in conjunction
with the accompanying drawings, in which:
FIG. 1 is a highly schematic block diagram of a vapor compression
distiller in accordance with the present invention;
FIG. 2 is a cross-sectional plan view of a single-effect, rotary
heat exchanger in accordance with the present invention;
FIG. 3A is a top view of a heat exchanger plate;
FIG. 3B is a side view of the plate of FIG. 3A along lines
3B--3B;
FIG. 4 is partial cross-sectional view of a series of plates the
heat exchanger of FIG. 2;
FIG. 5 is a partial cross-sectional plan view of a multiple-effect,
rotary heat exchanger in accordance with the present invention;
FIG. 6A is a top view of a transfer plate of the heat exchanger of
FIG. 5;
FIG. 6B is a side view of the transfer plate of FIG. 6A along lines
6B--6B; and
FIG. 7 is a cross-sectional plan view of the interface between two
effects of the heat exchanger of FIG. 5.
DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT
FIG. 1 is a schematic diagram of a vapor compression distillation
system 100 in accordance with the present invention. Generally, the
system 100 comprises a heat exchanger 102 for heating a supply of
liquid, such as non-potable water, to be distilled. Heated liquid
is transferred to an evaporation and condensation unit 104 by a
feed line 106. Coupled to the evaporation and condensation unit 104
are a motor 108 for supplying rotary power and a compressor 110,
which receives vapor generated within unit 104, compresses it and
returns it to unit 104. An output line 112 transfers a condensate,
such as distilled water, through the heat exchanger 102 and into a
holding tank 114.
Single-Effect System
FIG. 2 is a highly schematic, cross-sectional view of the
evaporation and condensation unit 104 of FIG. 1 configured as a
single effect system. The unit 104 includes a housing 202 having a
bottom wall 204, a top wall 206 and side walls 208. Disposed within
the housing 202 are a plurality of horizontally stacked
heat-exchange plates 210 which form a heat exchanger. The plates
210 are preferably sandwiched between a bottom end 212 proximate to
bottom wall 204 and a top end plate 214 proximate to top wall 206.
The plates 210 are also aligned for rotation about a common,
central axis A--A. A shaft 216 from motor 108 extends through the
bottom wall 204 of housing 202 and engages the bottom end plate 212
which may include a rotary drive adapter (not shown) or otherwise
be configured to receive shaft 216. A vapor outlet tube 218 couples
the housing 202 preferably at its top wall 206 to an inlet port 220
of the compressor 110. A vapor inlet tube 222 similarly connects
the housing 202 preferably at its top wall 206 to an outlet port
224 of the compressor 110. A sump 226 which receives a liquid to be
distilled from feed line 106 is located at the bottom of the
housing 202. Each plate 210 defines two surfaces 228, and the
oppositely facing surfaces 228 of adjacent plates 210 define spaces
therebetween. These spaces, moreover, are alternately configured as
evaporating chambers 230 and condensing chambers 232.
FIGS. 3A and 3B are top and side views, respectively, of a plate
210. Each plate 210 includes both an inner diameter edge 302 and an
outer diameter edge 304 relative to a center point P which also
corresponds to the axis of rotation A--A. Each plate 210 also
includes a plurality of ports for distributing liquid to be
distilled and for extracting a condensate from the unit 104, as
described below. In particular, each plate 210 includes at least
one liquid feed port 306 proximate to inner diameter edge 302 and
at least one condensate port 308 proximate to outer diameter edge
304. In the preferred embodiment, each plate 310 includes three
liquid feed ports 306 and three condensate ports 308. Each plate
210 further includes a restriction element 310 on one surface 228
thereof. The restriction element 310, which may be ring-shaped, is
located slightly outboard of the liquid feed ports 306 relative to
center point C and thus rotational axis A--A. The ring-shaped
restriction element 310 preferably extends completely around the
plate surface 228 at its respective radial location.
Returning to FIG. 2, the stacking arrangement of plates 210 within
housing 202 establishes a generally vertical liquid flow path,
designated generally by arrow F, along liquid feed ports 306 that
provides fluid communication with each evaporating chamber 230, but
by-passes the adjacent condensing chambers 232. The arrangement of
plates 210 similarly establishes a generally vertical condensate
flow path, designated generally by arrow C, along condensate ports
308 that provides fluid communication with each condensing chamber
232, but by-passes the evaporating chambers 230. Additionally, the
inner diameter edges 302 of adjacent plates 210 forming each
evaporating chamber 230 are sealed, while the inner diameter edges
302 of adjacent plates 210 forming each condensing chambers 232 are
open to receive compressed vapor, as described below. Similarly,
the outer diameter edges 304 of adjacent plates 210 forming each
evaporating chamber 230 are open to the housing 202 to discharge
vapor and liquid therein, while the outer diameter edges 304 of
adjacent plates 210 forming each condensing chambers 232 are
sealed.
A rotary scoop tube 234 having a scoop end 234a extends from a
lowest evaporating chamber 230 in the stack through bottom end
plate 212 and into the sump 226. In particular, rotary scoop tube
234 is coupled to the lowest evaporating chamber 230 at its liquid
feed port 306. Top end plate 214 includes a condensate port 236
that is preferably axially aligned with the condensate ports 308 of
the stack of plates 210. A flange 238 is preferably mounted to an
outer edge 214a of top end plate 214 opposite to the stack of
plates 210 so as to define a collection space 240 between flange
238 and top end plate 214 opposite the stack of plates 210 at the
upper most condensing chamber 232. A stationary scoop tube 242
having a scoop end 242a extends through top wall 206 of housing 202
such that scoop end 242a is disposed in the collection space 240.
The stack of plates 210 within housing 202 also defines a centrally
located compressed vapor receiving space 244 inboard of the inner
diameter edges 302 of plates 210 and a vapor collection space 246
between the outer edges 304 of plates 210 and the side walls 208 of
housing 202.
In the preferred embodiment, plates 210 are formed from 0.008 inch
copper sheet stock, although other materials having sufficiently
high thermal conductivity, such as stainless steel, may also be
used. The plates 210 also have an inside diameter of approximately
three inches and an outside diameter of approximately ten inches.
The liquid feed ports 306 and condensate ports 308 each have
cross-sectional areas on the order of 0.1 to 0.5 square inches and
are generally elliptically shaped with the major axis substantially
circumferentially aligned, although other shapes, such as circular,
may also be employed. Other plate dimensions may be used depending
on the desired condensation flow rate of the distiller 100. The
inner diameter edges 302 of evaporating chambers 230 and the outer
diameter edges 304 of condensing chambers 232 are preferably welded
or braised together so that the stack of plates 210 is essentially
bellows-shaped. The width of the evaporating and condensing
chambers 230, 232 may be on the order of 0.02 to 0.2 inches. Each
plate surface 228, moreover, may include a plurality of raised
dimples (not shown) which contact the opposing plate surface 228
and thereby maintain the desired spacing between adjacent plates
210.
A suitable compressor 110 for use with the present invention is
disclosed in a copending U.S. Patent Application (Attorney Docket
No. 98-01 -BZ), entitled A Reciprocating Low Pressure Ratio
Compressor, filed the same day as and commonly owned with the
present application and hereby incorporated by reference in its
entirety. A suitable motor 108 for use with the present invention
is a two or four pole electrical motor which may have an operating
speed in the range of 1500-3600 rpm.
In operation, motor 108 is activated, thereby rotating shaft 216,
which, in turn, rotates the stack of plates 210 within housing 202
at approximately 1000 rpm by using a conventional speed reducer
(such as a belt or gear transmission). Liquid to be distilled, such
as non-potable water, passes through heat exchanger 102, where it
is heated approximately to the boiling point and flows through
inlet pipe 106 to the sump 226 of the evaporation and condensation
unit 104. Compressor 110 is also activated, thereby drawing any
vapor from housing 202 through outlet tube 218 and into the
compressor inlet 220. Compressed vapor is fed to the central
receiving space 244 of the housing 202 through inlet tube 222.
Rotation of the stack of plates 210 also causes the rotary scoop
234 to rotate through the sump 226. With the scoop end 234a below
the surface of the sump 226 and open in the direction of rotation,
rotation of the scoop 234 causes a column of liquid to be forced up
the scoop 234, through bottom end plate 212 and into the lowest
evaporation chamber 230 via its respective liquid feed port
306.
FIG. 4 is an enlarged cross-sectional view of several stacked
plates 210 illustrating the corresponding fluid flow patterns. As
shown by arrow F, liquid from sump 226 is forced up through the
liquid feed ports 306 within each plate 210 and enters each
evaporating chamber 230. Due to the centrifugal forces generated
within the rotating stack of Is plates 210, liquid is forced
through the restriction element 310, where it is converted into
sheets (as opposed to discrete streams) that flow along each of the
oppositely facing plate surfaces 228 within the respective
evaporating chamber 230. The restriction element 310 may also meter
the flow of liquid through the respective evaporating chamber 230
such that liquid is received through port 306 faster than it flows
through the respective evaporation chamber 230. Accordingly, an
annular pool of liquid, designated L, forms within the entrance of
the lowest evaporating chamber 230. Liquid continues to build up
within the entrance, until the surface of the pool L reaches the
outboard edge of the liquid feed port 306 relative to the axis of
rotation A--A. When the height of the pool L reaches this point,
additional liquid received in the evaporation chamber 230 will flow
upwardly through the liquid feed port 306 and into the next highest
evaporating chamber 230. Because liquid enters this next highest
evaporating chamber 230 faster than it passes through the
corresponding restriction element 310, another annular pool L is
formed. This process is repeated at each evaporating chamber 232
within the stack of plates 210, thereby forcing liquid upwardly
from the sump 226 along the liquid flow path F and into each
evaporating chamber 230 where it forms a corresponding annular pool
L.
To prevent liquid from the sump 226 from entering the condensing
chambers 232 (and possibly contaminating the condensate being
formed therein), each plate surface 228 within the condensing
chambers 232 preferably includes a feed port flange 402 around the
corresponding liquid feed port 306. Each feed port flange 402
includes a distal surface 403 configured such that, when the plates
210 are assembled in a vertical stack arrangement, the two distal
surfaces 403 of opposing feed port flanges 402 within each
condensing chamber 232 join to provide a fluid seal. Opposing
distal surfaces 403 of adjacent feed port flanges 402 may be joined
by welding, braising, soldering or other suitable techniques.
Liquid flowing upwardly through the liquid flow path F is thus
unable to enter the condensing chambers 232. Because liquid is
intended to enter the evaporating chambers 230, flanges are not
provided around the liquid feed ports 306 in the evaporating
chambers 230.
In the preferred embodiment a feed tube (not shown) having an axial
slot is inserted through ports 306 along the liquid feed flow path
F such that the axial slot faces the axis of rotation A--A. Liquid
from sump 226 climbs and fills the feed tube. As additional liquid
is forced into the tube, the excess spills out of the open slot at
each evaporating chamber 230, flows through the restriction element
310 and enters the evaporating chamber 230. The use of such a feed
tube allows a much smaller column of water to formed at each
restriction element 310.
After passing the restriction element 310, liquid flows, preferably
in sheet form, along the opposing plate surfaces 228 within each
evaporating chamber 230. As described below, heat from the adjacent
condensing chambers 232 causes some portion of this liquid to
evaporate and form a vapor. The presence of annular pools L forces
the vapor to flow radially outward. Since the evaporating chambers
230 are open at their outboard ends, the vapor enters the housing
202 at the vapor collection space 246. Similarly, any remaining
liquid that was not converted to vapor is flung off of the plate
surfaces 228, strikes the side walls 208 of the housing 202 and
drops down into the sump 226. Operation of the compressor 110
causes the vapor formed in the evaporating chambers 230 and
discharged to the vapor collection space 246 to flow upwardly
through the housing 202 and into the outlet tube 218. The vapor is
then compressed within the compressor 110, which raises its
temperature and pressure. Compressed vapor is returned to the
housing 202 at the central receiving space 244 by inlet tube
222.
Compressed vapor enters the condensing chambers 232, which are open
to the central receiving space 244 at their inboard edges. Since
the liquid feed port flanges 402 only extend around the
corresponding liquid feed ports 306, they do not block the flow of
compressed vapor into the condensing chambers 232. As the liquid
flowing along plate surfaces 228 in the adjacent evaporating
chambers 230 is vaporizing at a lower temperature (e.g.,
212.degree. F.) than the compressed vapor (e.g., 214.degree. F.
saturation temperature), compressed vapor condenses along the
opposing plate surfaces 228 within the condensing chambers 232.
This condensate is forced to the outboard ends of the condensing
chambers 232 by the centrifugal forces generated through rotation
of the plates 210. Because the outboard ends of the condensing
chambers 232 are closed, the condensate forms annular pools,
generally designated P. As more and more vapor condenses within the
condensing chambers 232, the surfaces of these pools P start to
fill the condensate ports 308 beginning at the outboard edges
thereof.
The condensate, which is constantly seeking out a lower level
(relative to axis A--A), flows through the condensate port 236 at
top end plate 214 and spills into the collection space 240. Here,
condensate is removed by stationary scoop 242. More specifically,
the build-up of condensate in the collection space 240 will
eventually reach the scoop end 242a of the stationary scoop 242, at
which point condensate will be forced into the scoop 242 and
removed from the evaporating and condensing unit 104. By constantly
removing condensate from the collection space 240, a flow pattern
is established from the chambers 232 along the condensate flow path
C and into the collection space 240. The scoop end 242a of scoop
242 is preferably disposed within collection space 240 so that
condensate ports 308 remain full of condensate. The presence of
condensate filing the condensate flow path C blocks higher pressure
vapor in the condensing chambers 232 from simply flowing up through
ports 308 and entering housing 202 which contains lower pressure
vapor generated in the evaporating chambers 230.
To prevent condensate flowing along the condensate flow path C from
entering the adjacent evaporating chambers 230, each plate surface
228 within the evaporating chambers 230 preferably includes a
condensate port flange 404 around the corresponding condensate port
308. Each condensate port flange 404 also includes a distal surface
406 configured such that, when the plates 210 are assembled in a
vertical stack arrangement, the two distal surfaces 406 of opposing
condensate port flanges 404 within each evaporating chamber 230 are
joined to provide a fluid seal. Opposing distal surfaces 406 of
adjacent condensate port flanges 404 may similarly be welded,
braised, soldered or otherwise joined using suitable techniques.
Condensate flowing upwardly through the condensate flow path C is
thus unable to enter the evaporating chambers 230. Because
condensate is intended to enter the condensing chambers 232,
flanges are not provided around the condensate ports 308 in the
condensing chambers 232.
As shown, the fluid flow patterns established within the novel
evaporation and condensation unit 104 of the present invention
reduce the risk of contamination of the final condensate. First,
condensate is preferably drawn out of the unit 104 near the top
opposite the sump 226, thereby reducing the chance that liquid from
the sump 226 will contaminate the condensate. Additionally, leaks
in the condensing chambers 232 (e.g., due to improper sealing of
their outboard edges) only result in condensate entering the
housing 202 and falling down into the sump 226. Furthermore,
because the liquid feed ports 306 are located outboard from the
inner diameter edges of the evaporating chambers 230, liquid is
unlikely to flow against the centrifugal forces and enter the
central receiving space 244 even if an improper weld or braise were
present.
In the preferred embodiment, a pressure differential of
approximately 0.5 psi and a temperature differential of
approximately 2.degree. F. is established between the evaporating
and condensing chambers 230, 232 during steady state operation of
unit 104. This pressure differential, moreover, provides additional
safeguards during generation of potable, distilled water. In
particular, should a leak develop between adjacent chambers 230,
232, the pressure differential will cause condensate to enter the
evaporating chamber 230 while preventing "dirty" liquid from
entering the condensing chambers 232.
In the preferred embodiment, each restriction element 310 has a
generally trapezoidal cross-section and opposing restriction
elements 310 define a gap through which liquid flows. The gap is
preferably on the order of 0.002-0.010 inches (preferably 0.003
inches) and may be a function of the width of the corresponding
evaporating chambers 230. Nonetheless, it should be understood that
the restriction element 310 may take alternative forms. For
example, they may have semi-circular cross-sections. Alternatively,
the restriction elements 310 may extend across the entire width of
the corresponding evaporation chambers 230, but include a plurality
of relatively wide passages therethrough so that liquid may enter
the evaporation chambers 230.
It should also be understood that the system 100 preferably
includes one or more de-gasser components (not shown) for removing
air and other gases from the system 100.
Multiple-effect System
FIG. 5 is a highly schematic, cross-sectional view the evaporation
and condensation unit 104 of FIG. 1 configured as a multiple-effect
system. The unit 104 includes a housing 502 having a bottom wall
504, a top wall 506 and side walls 508. Disposed within the housing
502 are a plurality of horizontally stacked, spaced-apart
heat-exchange plates 510 arranged in a plurality of effects to form
a heat exchanger. The plates 510 are preferably sandwiched between
a bottom end plate 512 proximate to bottom wall 504 and a top end
plate 514 proximate to top wall 506. The plates 510 are also
aligned for rotation about a common, central axis A--A. A shaft 516
from motor 108, which in this embodiment may be mounted above the
housing 502, extends through top wall 506 and engages the top end
plate 514 which may include a rotary drive adapter (not shown). A
vapor outlet tube 518 couples the housing 502 preferably at its top
wall 506 to the compressor 110 (FIG. 1). The vapor outlet tube 518
is preferably centrally disposed to reduce the chances of liquid
being conveyed to compressor 110 along with vapor. A vapor inlet
tube 522 similarly connects the housing 502 preferably at its
bottom wall 504 to the compressor 110. A sump 526 which receives a
liquid to be distilled from feed line 106 is also located at the
bottom of the housing 502. Inlet tube 522 extends through sump 526.
Each plate 510 defines two surfaces 528, and the oppositely facing
surfaces 528 of adjacent plates 510 define spaces therebetween.
These spaces, moreover, are alternately configured within each
effect as evaporating chambers 530 and condensing chambers 532.
Within each effect, plates 510 are substantially similar in design
and configuration to plates 210 shown in FIGS. 3A and 3B. More
specifically, each plate 510 includes both an inner diameter edge
302 and an outer diameter edge 304, at least one liquid feed port
306 proximate to inner diameter edge 302 and at least one
condensate port 308 proximate to outer diameter edge 304. Each
plate 510 further includes a restriction element 310 on one surface
528 thereof. The stacking arrangement of plates 510 within each
effect establishes a generally vertical liquid flow path, F, along
liquid feed ports 306 within each effect that provides fluid
communication with each evaporating chamber 530, but bypasses the
adjacent condensing chambers 532, and a generally vertical
condensate flow path, C, along condensate ports 308 that provides
fluid communication with each condensing chamber 532, but by-passes
the evaporating chambers 530. Additionally, the inner diameter
edges 302 of adjacent plates 510 forming each evaporating chamber
530 are sealed, while the inner diameter edges 302 of adjacent
plates 510 forming each condensing chambers 532 are open to receive
vapor, as described below. Similarly, the outer diameter edges 304
of adjacent plates 510 forming each evaporating chamber 530 are
open, while the outer diameter edges 304 of adjacent plates 510
forming each condensing chamber 532 are sealed.
A rotary scoop tube 534 having a scoop end 534a extends from the
liquid feed port 306 of the lowest evaporating chamber 530 within
the first effect through bottom end plate 512 and into the sump
526. Top end plate 514 includes a condensate port 536 that is
preferably axially aligned with the condensate ports 308 of the
stack of plates 510. A flange 538 is preferably mounted to an outer
edge 514a of top end plate 514 opposite to the stack of plates 510
so as to define a collection space 540. A stationary scoop tube 542
having a scoop end 542a extends through top wall 506 such that
scoop end 242a is disposed in the collection space 540. The stack
of plates 510 within housing 502 also defines a central, compressed
vapor receiving space 544 inboard of the inner diameter edges 302
of plates 510.
An inner wall 550, which is generally disposed inboard of the inner
diameter edges of plates 510 (relative to axis of rotation A--A),
extends from the top end plate 514 to the upper most plate 510 of
the first effect. Inner wall 550 essentially blocks compressed
vapor in the central receiving space 544 from entering the
condensing chambers 532 of all but the first effect, as described
below. An outer wall 552, which is generally disposed outboard of
the outer diameter edges of plates 510 (relative to the axis of
rotation A--A), extends from the bottom end plate 512 to the lowest
plate of the highest effect (e.g., the third effect). The outer
wall 552, which includes an inner surface 552a, defines an enclosed
space 560 inboard of the side wall 508 and essentially blocks vapor
generated in the evaporating chambers 530 of all but the highest
effect from entering the housing 502, as described below. A
plurality of apertures 554 are provided in the outer wall 552 at
each effect.
Between the plates 510 comprising each effect is at least one
transition plate 556. That is, at least one transition plate 556 is
disposed between the first and second effect, between the second
and third effect and so on. As described below, the configuration
of transition plates 556 and walls 550 and 552 causes vapor
generated in the evaporating chambers 530 of a given effect (e.g.,
the first effect) to flow to the condensing chambers 532 of the
next highest effect (e.g., the second effect). They also permit
liquid to flow from the sump 526 to the evaporating chambers 530 of
each effect and the condensate generated in the condensing chambers
532 of each effect to flow to the collection space 540 where it may
be withdrawn by stationary scoop 542.
FIGS. 6A and 6B are top and side views, respectively, of a
transition plate 556. Each transition plate 556 includes both an
inner diameter edge 556a and an outer diameter edge 556b relative
to a center point P which also corresponds to the axis of rotation
A--A. Each transition plate 556 also includes a plurality of ports
for distributing liquid between adjacent effects and for conveying
condensate between adjacent effects. In particular, each transition
plate 556 includes at least one liquid transition port 602
proximate to inner diameter edge 556a and at least one condensate
transition port 604 proximate to outer diameter edge 556b. The
liquid transition port 602 and condensate transition port 604,
however, are slightly off-set from the corresponding liquid feed
ports 306 and condensate ports 308 of intra-effect plates 510. More
specifically, the liquid transition ports 602 are disposed slightly
inboard of the corresponding liquid feed ports 306 of plates 510.
Similarly, the condensate transition ports 604 of the transition
plates 556 are disposed slightly inboard of the corresponding
condensate ports 308. Preferably, there is no overlap between
transition ports 602, 604 and corresponding ports 306, 308.
In operation, motor 108 and compressor 110 are activated spinning
the stack of plates 510 and withdrawing low pressure vapor from the
housing 502 and returning higher pressure, higher temperature vapor
to the central receiving space 544. Rotating scoop 534 draws liquid
up from the sump 526 to the liquid feed port 306 of the lowest
evaporation chamber 530 in the first effect. As described above in
connection with the single effect system, liquid from sump 526
flows upwardly through the liquid feed channel F within the plates
510 of the first effect, thereby delivering liquid to each
evaporation chamber 530 within the first effect. Compressed vapor
from compressor 110 is delivered to central receiving space 544 and
enters the condensing chambers 532 of the first effect which are
open at their inner diameter edges to the central receiving space
544. Condensate forms along the plate surfaces 528 in the
condensing chambers 532 transferring heat to the adjacent
evaporating chambers 530. Vapor generated within the evaporating
chambers 530 and any remaining liquid are discharged into the
enclosed space 560 between the outer wall 552 and the outer
diameter ends of the evaporating chambers 530 of the first
effect.
Due to the centrifugal force generated within the rotating stack of
plates 510, unevaporated liquid forms an annular pool against an
inner surface 552a of the outer wall 552. A stream of liquid will
bleed out of this annular pool through the apertures 554 in the
outer wall 552 and fall down into the sump 526. The apertures 554
are preferably sized to permit an annular pool of liquid to remain
inside of the outer wall 552. That is, apertures 544 are configured
to remain full of liquid, thereby presenting a liquid barrier
between the vapor in enclosed space 560 and the housing 502. Vapor
thus flows upwardly to the transition plate 556 separating the
first and second effects.
FIG. 7 is a cross-sectional view of the interface between two
effects (e.g., the first and second effects) of the multiple-effect
system. As shown by arrow F, liquid from sump 526 is forced up
through the liquid feed ports 306 within each plate 510 of the
first effect and enters the corresponding evaporating chambers 530.
An annular pool of liquid L also forms within the entrance of each
evaporating chamber 530. Plates 510 similarly include feed port
flanges 402 around the liquid feed ports 306 and condensate port
flanges 404 around the condensate ports 308 with correspondingly
mating distal ends to prevent liquid from entering the condensing
chambers 532 and condensate from entering the evaporating chambers
530. The vapor from evaporating chambers 530 flows around the outer
edge 556b of the transition plate 556 which is preferably spaced
from the outer wall 552 and into a transition space 710 defined by
transition plate 556 and the first plate 510 of the next highest
effect (e.g., the second effect). The vapor then flows inwardly
along the transition space 710 to the inner diameter edges 302 of
the condensing chambers 532 of the next highest effect. The inner
diameter edge 556a of the transition plate 556 is preferably sealed
against the inner wall 550 to prevent compressed vapor from the
central receiving space 544 from flowing to the transition space
710. Instead, the vapor generated in evaporating chambers 530 of
the first effect is forced to enter the condensing chambers 532 of
the second effect.
Still considering the first effect, compressed vapor from central
receiving space 544 enters the condensing chambers 532, condenses
along the opposing plate surfaces 528 and is forced to the outboard
ends of the chambers 532 by centrifugal force. The condensate forms
annular pools, generally designated P, at the outboard ends of
chambers 532 which are sealed. Condensate flows through the
condensate ports 308 of plates 510 within the first effect toward
the transition plate 556. At the transition plate 556, a first
condensate sleeve 712 extends between transition plate 556 and the
adjacent plate 510 in the first effect around off-set ports 604 and
308. First condensate sleeve 712 seals the condensate flow path C
from the evaporating chamber 532 adjacent to transition plate 556.
The first condensate sleeve 712 preferably extends only around the
ports 604 and 308 and thus does not block the flow of vapor or
liquid in the respective evaporating chamber 532. A second
condensate sleeve 714 seals the condensate flow path C within the
transition space 710. In particular, second condensate sleeve 714
extends between transition plate 556 and the adjacent plate 510 in
the second effect and around off-set ports 604 and 308. A liquid
feed sleeve 716 similarly seals the liquid feed flow path F between
the transition plate 556 and the first plate 510 of the next
effect. The liquid feed sleeve 716 preferably extends only around
the off-set ports 602 and 306 so as to allow vapor from evaporating
chambers 530 to flow along transition space 710.
As described above in connection with FIGS. 6A and 6B, liquid
transition port 602 in transition plate 556 is axially off-set from
the corresponding ports 306 in plates 510, thereby defining a
liquid feed weir 718. Liquid flowing along the liquid feed flow
path F within the first effect must "climb" over this weir 718 in
order to reach the liquid feed flow path F within the second
effect. The column of liquid corresponding to weir 718 presents a
static head blocking vapor generated in the evaporating chambers
530 of the first effect from flowing along the liquid feed flow
path F to the second effect. Liquid flows along the liquid feed
flow path F within each effect, over the corresponding weir 718 at
each transition plate 556 and into the liquid feed flow path F of
the next highest effect. Liquid from sump 526 is thus distributed
to the evaporating chambers 530 at each effect. Similarly, a
condensate weir 720 is defined by the axially off-set arrangement
between condensate transition port 604 and ports 308 in plates 510.
Condensate flowing along the condensate flow path C in the first
effect must "climb" over this weir 720 in order to reach the
condensate flow path C in the second effect. The corresponding
column of condensate presents a static head blocking any vapor in
the condensing chambers 532 of the first effect from flowing along
the condensate flow path C to the higher effects. Condensate thus
flows along the condensate flow path C from the first effect up to
the highest effect in the unit 104. At the highest effect,
condensate flows through condensate poll 536 and accumulates in the
collection space 240 where it is removed by stationary scoop 542.
The end 242a of scoop 242 is again preferably positioned so that
the condensate ports defining the condensate flow path C remain
full of condensate.
It should be understood that the plate surfaces 228 within the
evaporating chambers 230 are preferably made hydrophilic while the
plate surfaces 228 in the condensing chambers 232 are made
hydrophobic. Due to its rotational speed, moreover, the plate stack
may be oriented in any direction.
It should be further understood that the evaporation and
condensation unit 104 may alternatively be thermally driven. More
specifically, liquid in the sump may be heated to generate vapor at
the desired saturation temperature by sources, such as a stove top
burner, solar energy, etc.
The foregoing description has been directed to specific embodiments
of this invention. It will be apparent, however, that other
variations and modifications may be made to the described
embodiments, with the attainment of some or all of their
advantages. For example, although the present invention has been
described in connection with a system for generating potable water,
other uses of the evaporation and condensation unit, such as
separating two liquids, may be made. Therefore, it is the object of
the appended claims to cover all such variations and modifications
as come within the true spirit and scope of the invention.
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